VEGF isoforms and their use as anti-angiogenic, anti-vasodilatory, anti-permeability and anti-proliferative agents

ABSTRACT

An isolated VEGF polypeptide having anti-angiogenic activity, said polypeptide including the amino acid sequence of SEQ. ID NO. 1, or variants thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 National Phase Entry Application of co-pending International Application PCT/GB02/03213, filed 12 Jul. 2002 which designated the U.S. and which claims the benefit under 35 U.S.C. §119 of GB application 0118836.6, filed 1 Aug. 2001 and GB application 0202817.3, filed 6 Feb. 2002.

The present invention relates to novel VEGF isoforms and their use as anti-angiogenic, anti-vasodilatory, anti-permeability and anti-proliferative agents and inhibition of such isoforms in conditions in which their expression in excess may be associated with disease states.

In order for tissue to grow it needs to develop and maintain an active and highly efficient blood supply from the surrounding vasculature. This process (angiogenesis) is necessary for progression and survival of tumours, development of rheumatoid arthritis, psoriasis, proliferative eye disease and a host of other pathologies. A number of new anti-tumour therapies are being developed that target this novel vasculature, or the growth factors that produce it. This is of particular interest in cancer research. This novel approach to cancer therapy contrasts with traditional chemotherapeutic strategies which target cell proliferation. The advantage of this approach lies in the distinction that angiogenesis is not an essential component of normal physiology (except in the development of the corpus luteum, endometrium and placenta in pre-menopausal women), and therefore anti-angiogenesis is not as toxic as anti-proliferative therapies, which also affect hair growth, normal gastrointestinal physiology, skin epidermis and many other normal aspects of physiology. The therapeutic dose of anti-angiogenics is therefore predicted to be well below the most tolerated doses, unlike anti-proliferative drugs. Tumours develop and maintain their new blood supply by secreting endothelial cell-specific growth factors, a number of which have been isolated in the last few years. One of these is Vascular Endothelial Growth Factor (VEGF), a naturally secreted protein that stimulates angiogenesis, vasodilatation and increased vascular permeability in vivo.

Vascular endothelial growth factor (VEGF) is a 32-42 kDa dimeric glycoprotein which mediates vasodilatation, increased vascular permeability and endothelial cell mitogenesis. Differential exon splicing of the VEGF gene results in three main mRNA species which code for three secreted isoforms (subscripts denote numbers of amino acids): VEGF₁₈₉, VEGF₁₆₅, and VEGF₁₂₁. A number of minor splice variants have been described (VEGF₂₀₆, VEGF₁₈₃, VEGF₁₄₅ and VEGF₁₄₈) but their importance remains uncertain (FIG. 1). Each isoform has distinct properties and patterns of expression (Ferrara et al (1997) Endocr. Rev. 18, 4-25; Houck et al (1991) Mol. Endocrinol. 5, 1806-1814; Poltorak et al (1997) J. Biol. Chem. 272, 7151-7158; Simon et al (1995) Am. J. Physiol. 268, 240-250; Brown et al (1992) Kidney Int. 42, 1457-1461; Park et al (1993) Mol. Biol. Cell 4, 1317-1326; Kevt et al (1996) J. Biol. Chem. 271, 7788-7795; Jingling et al (1999) Invest Opthalmol Vis Sci 40(3):752-9; Plouet et al (1997) J. Biol. Chem 272, 13390-13396; and Whittle C et al Clin Sci (1999) 97, 303-312);. The various molecular forms of VEGF share a common amino-terminal domain consisting of 110 amino acids, but differ in the length of the carboxyl-terminal portion and the final 6 amino acid residues (coded for by exon 8) are identical in all isoforms previously described except VEGF₁₄₈.

VEGF is known to promote vascular endothelial cell proliferation and angiogenesis, which are important components of a variety of pathologies, including tumour growth and metastasis, rheumatoid arthritis, atherosclerosis and arteriosclerosis (Celleti et al Nature 2001; 7. 425-9; Lemstrom et al 2002, 105. 2524-2530), neointimal hyperplasia, diabetic retinopathy and other complications of diabetes, trachoma, retrolental fibroplasia, neovascular glaucoma, age-related macular degeneration, trachoma haemangiomata, immune rejection of transplanted corneal tissue, corneal angiogenesis associated with ocular injury or infection, psoriasis, gingivitis and other conditions known to be associated with angiogenesis and/or chronic inflammation. Corneal angiogenesis associated with ocular injury or infection may be caused, for example, by Herpes or other viral or microbial infection.

In addition VEGF expression and angiogenesis are increased during fat deposition in animal models (Fredriksson et al (2000), J. Bio. Chem. 275(18): 13802-11; Asano et al (1999) J. Vet. Med. Sci. 61(4):403-9; Tonello et al (1999) FEBS Lett 442(2-3): 167-72; Asano et al (1997) Biochem. J. 328(Pt.1): 179-83), and it is therefore possible that anti-angiogenic agents may be used for reducing fat deposition and for fat reduction.

VEGF may also mediate pre-eclampsia (Brockelsby et al 1999, Lab Invest 79:1101-11). Pre-eclampsia is a condition of pregnancy characterised by high blood pressure, persistent excessive swelling of the hands, feet, ankles and sometimes face, and protein in the urine. If not diagnosed and treated quickly, it can lead to eclampsia, where a seizure occurs, coupled with a sharp rise in blood pressure and serious risk of stroke, as well as extreme distress to an unborn baby. Dysregulation of vasoconstriction/vaso-dilatation is known to be an important component of pre-eclampsia. Despite the fact that VEGF has been implicated in pre-eclampsia, one paradox is as yet unexplained; pre-eclampsia is associated with hypertension and vasoconstriction but VEGF₁₆₅ is a well known vasodilator.

VEGF also increases endothelial permeability which is an important component of a different variety of conditions including angiogenesis related oedema (i.e. in tumours), septicaemic/endotoxaemic shock, nephrotic syndrome, lymphoedema, burns and adult respiratory distress syndrome (ARDS) and pre-eclampsia as above.

The endothelial proliferative activity of VEGF is mediated by two high affinity membrane-bound tyrosine kinase receptors: VEGF receptor 1 (VEGFR₁, flt-1(fms-like tyrosine kinase-1)); and VEGF receptor 2 (VEGFR₂, flk (foetal liver kinase), KDR (Kinase domain containing receptor)). These receptors are expressed by vascular endothelial cells.

It is believed that normally both of the VEGF receptors are stimulated by a homodimer of VEGF monomers interacting with a homodimer of receptor molecules.

In view of the implied role of VEGF-mediated receptor stimulation in various diseases, there is considerable interest in developing inhibitors that would interfere with or modulate the interaction between VEGF and its receptor.

The major obstacle to the development of novel anti-angiogenic drugs in oncology and other specialities, however, has been the difficulty in obtaining angiogenic-specific inhibitors with acceptable half lives, solubility, specificity and immunotolerance.

Tissues are normally in an angiogenesis equilibrium, i.e. growth factors which stimulate new vessel growth are balanced by other factors which inhibit vessel growth (M. L. IruelaArispe and H. F. Dvorak, (1997) Thrombosis and Haemostasis. (78): 672-677). One of the tissues in which VEGF is normally most highly expressed is in the kidney glomerulus (L. F. Brown, et al., (1992) Kidney Int. (42):1457-61 E. Bailey 1999 J Clin Pathol 52, 735-738.). This tissue expresses high levels of VEGF, has very high endothelial permeability (an action of VEGF), but has low levels of angiogenesis. The reason for the high VEGF expression levels in kidney is not known but the high permeability of the endothelium and high glomerular filtration rate both appear to depend on VEGF (B. Klanke, et al., (1998) Nephrol Dial Transplant, (13):875-850) (C. Whittle, et al., (1999) Clin Sci (Colch). (97):303-12). It is not understood why there is no angiogenesis in kidneys in the presence of such high expression of VEGF.

The present inventors have identified a new isoform of VEGF in kidney cells, which is differentially spliced into a previously undescribed exon, exon 9. This novel isoform has been designated VEGF₁₆₅b.

According to a first aspect of the invention, there is provided an isolated VEGF polypeptide having anti-angiogenic activity, said polypeptide including the amino acid sequence of SEQ.ID NO.1, or variants thereof.

This unexpected anti-angiogenic property of the polypeptide of the first aspect of the present invention contrasts completely with the properties of all previously described VEGF isoforms which are pro-angiogenic.

The term “isolated” as used herein means altered from its natural state, i.e., if it occurs in nature, it has been changed or removed from its original environment, or both. For example, a polynucleotide or a polypeptide naturally present in a living organism is not “isolated”, but the same polynucleotide or polypeptide separated from the coexisting materials of its natural state is “isolated”, as the term is used herein. Moreover, a polynucleotide or polypeptide that is introduced into an organism by transformation, genetic manipulation or by another recombinant method is “isolated” even if it is still present in said organism, which organism can be living or non-living.

The term “variant(s)” as used herein, is a polynucleotide or polypeptide that differs from a reference polynucleotide or polypeptide respectively, but retains essential properties. A typical variant of a polynucleotide differs in nucleotide sequence from another, reference polynucleotide. Changes in the nucleotide sequence of the variant may or may not alter the amino acid sequence of a polypeptide encoded by the reference polynucleotide. Nucleotide changes may result in amino acid substitutions, additions, deletions, fusions and/or truncations in the polypeptide encoded by the reference sequence, as discussed below. A typical variant of a polypeptide differs in amino acid sequence from another reference polypeptide. Generally, differences are limited so that the sequences of the reference polypeptide and the variant are closely similar overall and, in many regions, identical. A-variant and reference polypeptide may differ in amino acid sequence by one or more substitutions, additions, and/or deletions in any combination. A substituted or inserted amino acid residue may or may not be one encoded by the genetic code. The present invention also includes variants of each of the polypeptides of the invention, that is polypeptides that vary from the references by conservative amino acid substitutions, whereby a residue is substituted by another with like characteristics. Typical conservative amino acid substitutions are among Ala, Val, Leu and Ile; among Ser and Thr; among the acidic residues, Asp and Glu; among Asn and Gln; and among the basic residues Lys and Arg; or aromatic residues Phe and Tyr. Such conservative mutations include mutations that switch one amino acid for another within one of the following groups:

1. Small aliphatic, nonpolar or slightly polar residues: Ala, Ser, Thr, Pro and Gly;

2. Polar, negatively charged residues and their amides: Asp, Asn, Glu and Gln;

3. Polar, positively charged residues: His, Arg and Lys;

4. Large aliphatic, nonpolar residues: Met, Leu, Ile, Val and Cys; and

5. Aromatic residues: Phe, Tyr and Trp.

Such conservative variations can further include the following:

Original Residue Variation Ala Gly, Ser Arg Lys Asn Gln, His Asp Glu Cys Ser Gln Asn Glu Asp Gly Ala, Pro His Asn, Gln Ile Leu, Val Leu Ile, Val Lys Arg, Gln, Glu Met Leu, Tyr, Ile Phe Met, Leu, Tyr Ser Thr Thr Ser Trp Tyr Tyr Trp, Phe Val Ile, Leu

The types of variations selected can be based on the analysis of the frequencies of amino acid variations between homologous proteins of different species developed by Schulz et al. (Principles of Protein Structure, Springer-Verlag, 1978), on the analyses of structure-forming potentials developed by Chou and Fasman (Biochemistry 13:211, 1974 and Adv. Enzymol., 47:45-149, 1978), and on the analysis of hydrophobicity patterns in proteins developed by Eisenberg et al. (Proc. Natl. Acad. Sci. USA 81:140-144, 1984), Kyte & Doolittle (J. Molec. Biol. 157: 105-132, 1981), and Goldman et al. (Ann. Rev. Biophys. Chem. 15:321-353, 1986). Particularly preferred are variants in which several, e.g., 5-10, 1-5, 1-3, 1-2 or 1 amino acids are substituted, deleted, or added in any combination. A variant of a polynucleotide or polypeptide may be naturally occurring such as an allelic variant, or it may be a variant that is not known to occur naturally. Non-naturally occurring variants of polynucleotides and polypeptides may be made by mutagenesis techniques, by direct synthesis, and by other recombinant methods known to a person skilled in the art.

The term “nucleotide(s)” as used herein generally refers to any polyribonucleotide or polydeoxyribonucleotide, which may be unmodified RNA or DNA or modified RNA or DNA. Polynucleotide(s) include, without limitation, single- and double-stranded DNA, DNA that is a mixture of single- and double-stranded regions or single- and triple-stranded regions, single- and double-stranded RNA, and RNA that is a mixture of single- and double-stranded regions, hybrid molecules comprising DNA and RNA that can be single-stranded or, more typically, double-stranded, or triple-stranded regions, or a mixture of single- and double-stranded regions. As used herein, the term “polynucleotide(s)” also includes DNAs or RNAs as described above that contain one or more modified bases. Thus, DNAs or RNAs with backbones modified for stability or for other reasons are “polynucleotide(s)” as the term is intended herein. Moreover, DNAs or RNAs comprising unusual bases, such as inosine, or modified bases, such as tritylated bases, to name just two examples, are polynucleotides as the term is used herein. It will be appreciated that a great variety of modifications have been made to DNA and RNA that serve many useful purposes known to those of skill in the art. The term “polynucleotide(s)” as used herein embraces such chemically, enzymatically or metabolically modified forms of polynucleotides, as well as the chemical forms of DNA and RNA characteristic of viruses and cells, including, for example, simple and complex cells. “Polynucleotide(s)” also embraces short polynucleotides often referred to as oligonucleotide(s).

The term “polypeptide(s)” as used herein refers to any peptide or protein comprising two or more amino acids joined to each other by peptide bonds or modified peptide bonds. “Polypeptide(s)” refers to both short chains, commonly referred to as peptides, oligopeptides and oligomers and to longer chains generally referred to as proteins. Polypeptides.can contain amino acids other than the 20 gene encoded amino acids. “Polypeptide(s)” include those modified either by natural processes, such as processing and other post-translational modifications, but also by chemical modification techniques. Such modifications are well described in research literature, and are well known to those skilled in the art. It will be appreciated that the same type of modification can be present at the same or varying degrees at several sites in a given polypeptide. Also, a given polypeptide can contain many types of modification. Modification can occur anywhere in a polypeptide, including the peptide backbone, the amino acid side-chains, and the amino or carboxyl termini. Modifications include, for example, acetylation, acylation, ADP-ribosylation, amidation, covalent attachment of flavin, covalent attachment of a heme moiety, covalent attachment of a nucleotide or a nucleotide derivative, covalent attachment of a lipid or lipid derivative, covalent attachment of phosphotidylinositol, cross-linking, cyclization, disulfide bond formation, demethylation, formation of covalent cross-links, formation of cysteine, formation of pyroglutamate, formylation, gamma-carboxylation, GPI anchor formation, hydroxylation, iodination, methylation, myristoylation, oxidation, proteolytic processing, phosphorylation, prenylation, racemization, glycosylation, lipid attachment, sulfation, gamma-carboxylation or glutamic acid residues, hydroxylation and ADP-ribosylation, selenoylation, sulfation, transfer-RNA mediated addition of amino acids to proteins, such as arginylation, and ubiquitination. See, for instance, PROTEINS—STRUCTURE AND MOLECULAR PROPERTIES, 2^(nd) Ed., T. E. Creighton, W. H. Freeman and Company, New York (1993) and Wold, F., Posttranslational Protein Modifications: Perspectives and Prospects. pgs 1-12 in POSTTRANSLATIONAL COVALENT MODIFICATION OF PROTEINS, B. C. Johnson. Ed., Academic Press, New York (1983); Seifter et al., Meth. Enzymol. 182:626-646 (1990) and Rattan et al., Protein Synthesis: posttranslational Modifications and Aging, Ann. N.Y. Acad. Sci. 663: 48-62 (1992). Polypeptides can be branched, or cyclic, with or without branching. Cyclic, branched and non-branched polypeptides can result from post-translational natural processes and can be made by entirely synthetic methods as well.

Preferably, at least a portion of the polypeptide comprises at least 66% identity to the sequence shown in SEQ.ID NO.1. More preferably, a least a portion of the polypeptide comprises at least 83% identity to the sequence shown in SEQ.ID NO.1.

Identity, as used herein, is a relationship between two or more polypeptide sequences or two or more polynucleotide sequences, as determined by comparing the sequences. In the art, “identity” also means the degree of sequence relatedness between polypeptide or polynucleotide sequences, as the case may be, as determined by the match between strings of such sequences. “identity” and “similarity” can be readily calculated by known methods, including but not limited to those described in (Computational Molecular Biology, Lesk, A. M., ed., Oxford University Press, New York, 1988; Biocomputing: Informatics and genome Projects, Smith, D. W., ed., Academic Press, New York. 1993; Computer Analysis of sequence Data, Part I, Griffin, A. M., and Griffin, H. G., eds., Humana Press. New jersey, 1994; sequence Analysis in Molecular Biology, von Heinje, G., Academic Press, 1987; and sequence Analysis Primer, Gribskov, M. and Devereux, J., eds., M Stockton Press, New York, 1991; and Carillo, H., and Lipman, D., SIAM J. Applied Math., 48:1073 (1998). Methods to determine identity are designed to give the largest match between the sequences tested. Moreover, methods to determine identity are codified in publicly available computer programs. Computer program methods to determine identity between two sequences include, but are not limited to, the GCG program package (Devereux, J., et al., Nucleic Acids Research 12(1): 387 (1984)), BLASTP, BLASTN, and FASTA (Altschul, S. F. et al., J. Molec. Biol. 215: 403-410 (1990). The BLAST X program is publicly available from NCBI and other sources (BLAST Manual, Altschul, S., et al., NCBI NLM NUH Bethesda, Md. 20894; Altschul, S., et al., J. Mol Biol. 215: 403-410 (1990).

Parameters for polypeptide sequence comparison include the following:

Algorithm: Needleman and Wunsch, J. Mol Biol. 48:443-453 (1970)

Comparison matrix: BLOSSUM62 from Hentikoff & Hentikoff, Proc. Natl. Acad. Sci. USA. 89:10915-10919 (1992)

Gap Penalty: 12

Gap Length Penalty: 4

A program useful with these parameters is publicly available as the “gap” program from Genetics Computer Group, Madison Wis. The aforementioned parameters are the default parameters for peptide comparison (along with no penalty for end gaps). In all cases where a computer program that does not necessarily give the maximized alignment discussed above is used to determine a measure of identity, the default parameters are preferred. Parameters for polynucleotide comparison include the following: Algorithm; Needleman and Wunsch, J. Mol Biol. 48: 443-453 (1970)

Comparison matrix: matches=+10, mismatch=0

Gap Penalty: 50

Gap Length Penalty: 3

Preferably, the sequence shown in SEQ ID NO. 1, or variants thereof, occurs at the C-terminus of the polypeptide.

Preferably, the polypeptide lacks exon 8. This will result in a polypeptide either lacking or having altered mitotic signalling compared to polypeptides containing exon 8.

A further aspect of the invention provides an isolated polypeptide having anti-angiogenic activity, the polypeptide comprising the sequence shown in SEQ. ID NO. 3, and variants thereof.

A further aspect of the invention provides a nucleotide sequence capable of encoding a polypeptide according to a first or second aspect of the invention.

A further aspect of the invention provides an isolated nucleotide sequence encoding a polypeptide having anti-angiogenic activity, the nucleotide sequence comprising the sequence shown in SEQ. ID NO.2, or variants thereof.

A further aspect of the present invention provides an isolated nucleotide sequence encoding a polypeptide having anti-angiogenic activity, the nucleotide sequence comprising the sequence shown in SEQ. ID NO. 4, or variants thereof.

A further aspect of the present invention provides a polynucleotide comprising a nucleotide sequence that hybridises, particularly under stringent conditions, to a VEGF₆₅b nucleotide sequence, such as the nucleotide sequence shown in SEQ. 2.

As used herein the term “stringent conditions” means hybridisation occurring only if there is at least 83% identity between the sequences. A specific example of stringent hybridisation conditions is overnight incubation at 42° C. in a solution comprising: 50% formamide. 5×SSC (150 mM NaCl, 15 mM trisodium citrate), 50 mM sodium phosphate (pH 7.6), 5× Denhardt's solution, 10% dextran sulphate, and 20 micrograms/ml of denatured, sheared salmon sperm DNA, followed by washing the hybridisation support in 0.1×SSC at about 65° C. Hybridisation and wash conditions are well known and exemplified in Sambrook, et al., Molecular Cloning: A Laboratory Manual, Third Edition, Cold Spring Harbour, N.Y., (1989), particularly Chapter II therein. Solution hybridisation can also be used with the polynucleotide sequences provided by the invention.

A nucleotide sequence according to the invention may be used as a hybridisation probe for RNA, cDNA and genomic DNA to isolate full-length cDNAs and genomic clones encoding VEGF₁₆₅b and to isolate cDNA and genomic clones of other genes that have a high identity, particularly high sequence identity, to the VEGF₁₆₅b gene. Such probes will generally comprise at least 15 nucleotide residues or base pairs, and can have at least 18 nucleotide residues or base pairs.

Preferably, the polypeptide and nucleotide sequence of the present invention is a mammalian sequence, such as a primate, rodent, bovine or porcine sequence. More preferably, the sequence is derived from a human sequence. The nucleotide sequence may include, for example, unprocessed RNAs, ribozyme RNAs, hair-pin RNAs for use as interference RNAs, small interfering RNAs (siRNAs), mRNAs, cDNAs, genomic DNAs, B-DNAs, E-DNAs and Z-DNAs.

For recombinant production of the polypeptides of the invention, host cells can be genetically engineered to incorporate expression systems or portions thereof or polynucleotides of the invention. Introduction of a polynucleotide into a host cell may be effected by methods described in many standard laboratory manuals, such as Davis, et al., BASIC METHODS IN MOLECULAR BIOLOGY, (1986) and Sambrook, et al., MOLECULAR CLONING: A LABORATORY MANUAL, 2nd Ed., Cold Spring Harbour Laboratory Press, Cold Spring Harbour. N.Y. (1989), such as, calcium phosphate transfection, DEAE-dextran mediated transfection, transfection, microinjection, cationic lipid-mediated transfection, electroporation, transduction, scrape loading, ballistic introduction and infection.

Representative examples of appropriate hosts include bacterial cells, such as streptococci, staphylococci, enterococci E. coli, streptomyces, cyanobacteria, Bacillus subtilis; fungal cells, such as yeast, Kluveromyces, Saccharomyces, a basidiomycete, Candida albicans and Aspergillus; insect cells such as Drosophila S2 and Spodoptera Sf9; animal cells such as CHO, COS, HeLa, C127, 3T3, BHK, 293, CV-1 and Bowes melanoma cells; and plant cells.

A great variety of expression systems can be used to produce the polypeptides of the invention. Such vectors include, among others, chromosomal-, episomal- and viral-derived vectors, for example, vectors derived from plasmids, from bacteriophage, from transposons, from yeast episomes, from insertion elements, from yeast chromosomal elements, from viruses such as baculoviruses, papova viruses, such as SV40, vaccinia viruses, adenoviruses, adeno-associated viruses, fowl pox viruses, pseudorabies viruses, picomaviruses and retroviruses, and vectors derived from combinations thereof, such as those derived from plasmid and bacteriophage genetic elements, such as cosmids and phagemids. The expression system constructs can contain control regions that regulate as well as engender expression. Generally, any system or vector suitable to maintain, propagate or express polynucleotides or to express a polypeptide in a host can be used for expression in this regard. The appropriate DNA sequence can be inserted into the expression system by any of a variety of well-known and routine techniques, such as, for example, those set forth in Sambrook, et al., MOLECULAR CLONING: A LABORATORY MANUAL, (supra).

For secretion of a translated protein into the lumen of the endoplasmic reticulum, into the periplasmic space or into the extracellular environment, appropriate secretion signals can be incorporated into the expressed polypeptide. These signals can be endogenous to the polypeptide or they can be heterologous signals.

Polypeptides of the invention can be recovered and purified from recombinant cell cultures by well-known methods, including ammonium sulphate or ethanol precipitation, extraction such as acid extraction, anion or cation exchange chromatography, gel filtration, phosphocellulose chromatography, hydrophobic interaction chromatography, affinity chromatography, hydroxylapatite chromatography, lectin chromatography, preparative electrophoresis, FPLC (Pharmacia, Uppsala, Sweden), HPLC (e.g., using gel filtration, reverse-phase or mildly hydrophobic columns). Most preferably, high performance liquid chromatography is employed for purification. Well known techniques for refolding proteins can be employed to regenerate an active conformation after denaturation of the polypeptide during isolation and/or purification. In vitro activity assays for polypeptides according to the present invention include, tyrosine kinase receptor activation assays, endothelial cell proliferation (e.g. thymidine incorporation, cell number or BrDU incorporation), cell migration assays (including scratch assays), tube formation, gel invasion assays or pressure or wire myograph assays. In vivo assays include angiogenesis assays using rabbit corneal eye pocket, chick chorioallantoic membrane assays, dorsal skinfold chamber assays, functional blood vessel density, blood flow, blood vessel number, tumour implantation assays (syngeneic or heterogeneic), tumour growth or vessel density assays, growth factor induced assays in hamster cheek pouch, rat, mouse or hamster mesentery, or sponge implant assay (Angiogenesis protcols—Ed. J. Clifford Murray; Humana Press, Totowa, N.J.; ISBN 0-89603-698-7 (part of a Methods in Molecular Medicine series)).

A polypeptide, or polynucleotide comprising a nucleotide sequence, according to the present invention or variants thereof, or cells expressing the same can be used as immunogens to produce antibodies immunospecific for such polypeptides or nucleotide sequences respectively.

A further aspect of the invention provides an isolated VEGF polypeptide or an isolated nucleotide sequence according to a preceding aspect of the present invention for use as an active pharmaceutical substance.

The active pharmaceutical substance is preferably used in the treatment of angiogensis or permeability or vasodilatation-dependent disease conditions as detailed above. Preferably angiogenesis-dependent disease conditions such as tumour growth and metastasis, rheumatoid arthritis, atherosclerosis, neointimal hyperplasia, diabetic retinopathy and other complications of diabetes, trachoma, retrolental fibroplasia, neovascular glaucoma, age-related macular degeneration, trachoma, haemangioma, immune rejection of transplanted corneal tissue, corneal angiogenesis associated with ocular injury or infection, vascular disease, obesity, psoriasis, arthritis, gingivitis and pre-eclampsia.

A further aspect of the invention provides a use of an isolated VEGF polypeptide sequence or an isolated nucleotide sequence according to preceding aspects of the present invention for the preparation of a pharmaceutical composition for the treatment of angiogenesis-dependent disease conditions such as previously mentioned.

A further aspect of the invention provides a method for treating or preventing angiogenesis in a mammalian patient, comprising supplying to the patient a polypeptide comprising the sequence of a VEGF polypeptide according to a previous aspect of the invention.

Preferably, an isolated VEGF polypeptide according to a previous aspect of the invention is capable of heterodimerising with endogenous VEGF thereby preventing or reducing VEGF-mediated cell proliferation or by direct binding to receptor normally the ligand for endogenous VEGF.

A further aspect of the invention provides a method for treating or preventing angiogenesis in a mammalian patient, comprising supplying to the patient a polynucleotide comprising a nucleotide sequence according to a previous aspect of the invention.

A further aspect of the invention provides a method for preventing or reducing VEGF-mediated cell proliferation in a mammalian patient comprising supplying to the patient a polypeptide comprising the sequence of an isolated VEGF polypeptide according to a previous aspect of the invention.

A further aspect of the invention provides a method for preventing or reducing VEGF-mediated cell proliferation in a mammalian patient comprising supplying to the patient a polynucleotide comprising the sequence of an isolated nucleotide sequence according to a previous aspect of the invention.

A further aspect of the invention provides a method for preventing or reducing VEGF₁₆₅-mediated vasodilatation in a mammalian patient comprising supplying to the patient a polypeptide comprising the sequence of a VEGF polypeptide according to a previous aspect of the invention.

A further aspect of the invention provides a polypeptide comprising the sequence of a VEGF polypeptide according to a preceding aspect of the invention for use in the treatment of VEGF₁₆₅-mediated vasodilatation.

A further aspect of the invention provides a use of a polypeptide comprising the sequence of a VEGF polypeptide according to a preceding aspect of the invention for the preparation of a pharmaceutical composition for the treatment of VEGF₁₆₅-mediated vasodilatation.

A further aspect of the invention provides a method for preventing or reducing VEGF₁₆₅-mediated vasodilatation in a mammalian patient comprising supplying to the patient a polynucleotide comprising the sequence of an isolated nucleotide according to a preceding aspect of the invention.

A further aspect of the invention provides a polynucleotide comprising the sequence of a nucleotide according to a previous aspect of the invention for use in the treatment of VEGF₁₆₅-mediated vasodilatation. Conditions in which VEGF₁₆₅-mediated vasodilatation is observed include, for example, cancer, psoriasis, arthritis etc.

A further aspect of the invention provides a use of a polynucleotide comprising a nucleotide sequence according to a preceding aspect of the invention in the preparation of a pharmaceutical composition for the treatment of VEGF₁₆₅-mediated vasodilatation.

A further aspect of the invention provides a pharmaceutical composition comprising a polypeptide comprising the sequence of a VEGF polypeptide according to a previous aspect of the invention and a pharmaceutically acceptable diluent.

Preferably, the vasodilatation and/or angiogenesis is associated with hair growth, as seen, for example, in hirsuitism. Any reduction in vasodilatation and/or angiogenesis would result in hair loss (Yano et al J Clin Invest (2001), 107 409-17).

A further aspect of the invention provides a pharmaceutical composition comprising a polynucleotide comprising a nucleotide sequence according to a previous aspect of the invention and a pharmaceutically acceptable diluent.

A further aspect of the invention provides an antibody raised against a VEGF polypeptide or nucleotide sequence according to a previous aspect of the invention.

Antibodies generated against the polypeptides or polynucleotides of the invention can be obtained by administering the polypeptides or polynucleotides of the invention, or epitope-bearing fragments of either or both, analogues of either or both, or cells expressing either or both, to an animal, preferably a nonhuman, using routine protocols. For preparation of monoclonal antibodies, any technique known in the art that provides antibodies produced by continuous cell line cultures can be used. Examples include various techniques, such as those in Kohler, G. and Milstein, C., Nature 256: 495-497 (1975); Kozbor et al., Immunology Today 4: 72 (1983); Cole et al., pg. 77-96 in MONOCOLONAL ANTIBODIES AND CANCER THERAPY, Alan R. Liss, Inc. (1985).

Techniques for the production of single chain antibodies (U.S. Pat. No. 4,946,778) can be adapted to produce single chain antibodies to polypeptides or polynucleotides of this invention. Also, transgenic mice, or other organisms such as other mammals, can be used to express humanized antibodies immunospecific to the polypeptides or polynucleotides of the invention.

Alternatively, phage display technology can be utilized to select antibody genes with binding activities towards a polypeptide of the invention either from repertoires of PCR amplified v-genes of lymphocytes from humans screened for possessing anti-VEGF₁₆₅b or from libraries (McCafferty, et al., (1990), Nature 348, 552-554; Marks, et al., (1992) Biotechnology 10, 779-783). The affinity of these antibodies can also be improved by, for example, chain shuffling (Clackson et al., (1991) Nature 352:628).

The above-described antibodies can be employed to isolate or to identify clones expressing the polypeptides or polynucleotides of the invention to purify the polypeptides or polynucleotides by, for example, affinity chromatography.

The polynucleotides, polypeptides and antibodies that bind to or interact with a polypeptide of the present invention can also be used to configure screening methods for detecting the effect of added compounds on the production of mRNA or polypeptide in cells. For example, an ELISA assay can be constructed for measuring secreted or cell associated levels of polypeptide using monoclonal and polyclonal antibodies by standard methods known in the art. This can be used to discover agents which can inhibit or enhance the production of polypeptide (also called antagonist or agonist, respectively) from suitably manipulated cells or tissues.

The invention also provides a method of screening compounds to identify those which enhance (agonist) or block (antagonist) the anti-angiogenic action of VEGF₁₆₅b polypeptides or polynucleotides. The method of screening can involve high-throughput techniques. For example, to screen for agonists or antagonists, a synthetic reaction mix, a cellular compartment, such as a membrane, cell envelope or cell wall, or a preparation of any thereof, comprising VEGF₁₆₅b polypeptide and a labelled substrate or ligand of such polypeptide is incubated in the absence or the presence of a candidate molecule that may be a VEGF₁₆₅b agonist or antagonist. The ability of the candidate molecule to agonize or antagonize the VEGF₁₆₅b polypeptide is reflected in decreased binding of the labelled ligand or decreased production of product from such substrate. Molecules that bind gratuitously, i.e., without inducing the anti-angiogenic effects of VEGF₁₆₅b polypeptide are most likely to be good antagonists. Molecules that,bind well and increase the anti-angiogenic effects of VEGF₁₆₅b are agonists. Detection of the increase in anti-angiogenic action can be enhanced by using a reporter system. Reporter systems that can be useful in this regard include but are not limited to colorimetric, labelled substrate converted into product, a reporter gene that is responsive to changes in VEGF₁₆₅b polynucleotide or polypeptide activity, and binding assays known in the art.

The invention further provides an inhibitor of a VEGF polypeptide according to a preceding aspect of the invention, for use in the treatment of vasoconstriction.

As pre-eclampsia results from poor placental invasion, i.e. a failure of angiogenesis, and VEGF antibodies have been shown to block the cause of hypertension in pre-eclampsia (Brockelsby et al Lab Invest 1999; 79:1101-11) this is considered by the present inventors to be potentially caused by excess new variant VEGF₁₆₅b, and thus inhibition of this new variant VEGF₁₆₅b, is expected to provide a treatment for pre-eclampsia.

It is presently believed that the inhibitor is capable of binding endogenous VEGF₁₆₅b, thereby preventing or reducing VEGF₁₆₅b-mediated vasoconstriction where vasoconstriction is associated with pre-eclampsia, and thus may be due to excess VEGF₁₆₅b expression.

The inhibitor may comprise an antibody according to a preceding aspect of the invention, for example, the inhibitor may be an exon 9 specific neutralising antibody.

Alternatively, the inhibitor may be a polynucleotide having a complementary sequence to the sequence of an isolated polynucleotide according to a previous aspect of the invention.

Inhibitors or VEGF₁₆₅b may be identified in suitable screens in which a candidate compound is screened for its ability to inhibit VEGF₁₆₅b. Such screens may be-carried out in respect of a plurality of compounds, for example, from a compound library.

An inhibitor identified using such a screen may be synthesised and formulated into a pharmaceutical composition for use.

The present invention also provides a method for preventing or reducing vasoconstriction in a mammalian patient comprising supplying to the patient an inhibitor according to a preceding aspect of the invention.

The present invention also provides a use of an inhibitor according to a previous aspect of the invention for the preparation of a pharmaceutical composition for the treatment of vasoconstriction.

The invention also provides an assay for the specific detection of VEGF_(165b) in a sample comprising carrying out a polymerase chain reaction on at least a portion of the sample, using an annealing temperature of at least 59° C. and the following primer sequences:

(SEQ ID NO: 1) exon 4 (forward primer): GAGATGAGCTTCCTACAGCAC (SEQ ID NO: 2) 9H (reverse primer): TTAAGCTTTCAGTCTTTCCTGGTGAGAGATCTGCA or variants thereof, wherein the variants retain the same annealing properties with respect to the VEGF₁₆₅b nucleotide sequence as the above primers.

This method allows the specific detection of VEGF₁₆₅b in a sample, even when the sample contains both VEGF₁₆₅b and VEGF₁₆₅.

Preferably, an annealing temperature of 60° C. is used.

Preferably, the method can detect VEGF₁₆₅b in a sample containing VEGF₁₆₅ at a concentration of up to 100 times greater, and preferably up to 500 times greater, more preferably 1000 times greater than the concentration of VEGF₁₆₅b in the sample.

A further aspect of the invention provides an isolated VEGF nucleotide sequence according to the present invention for use in the detection of exon 9 containing VEGF isoforms by quantitative real-time PCR. A number of technologies are available and known to those skilled in the art, these technologies would for example include but not be limited to: Taqman, Scorpion, Molecular Beacon (FRET).

In preceding aspects of the invention, VEGF₁₆₅b or its inhibitor is preferably supplied to a patient by injection. Preferably, VEGF is supplied to a patient by intra-arterial, intravenous, intramuscular, intra-peritoneal or subcutaneous injection. However when local application is required a regional injection may be preferable, and this can be inferred from the site of the disease process eg intra-articular or intra-orbital injection. Alternatively, VEGF₁₆₅b or inhibitor thereof may be supplied orally or topically. For example, in the treatment of gingivitis, VEGF₁₆₅b could be supplied orally in the form of a toothpaste or mouthwash containing VEGF₁₆₅b. For psoriasis VEGF₁₆₅b could be contained within an emollient cream, for herpes ocular infection in the form of eye-drops or cream, for pulmonary lesions in a nebulized aerosol.

The combination of VEGF₁₆₅b with other agents for simultaneous administration to a mammalian patient via any of the aforementioned routes in any clinical situation in which the simultaneous administration may be deemed beneficial in the light of the poperties of VEGF₁₆₅b and the other agent or agents. Specific combinations of VEGF₁₆₅b and another agent or agents would be apparent to the skilled person from the particular clinical situation involved. For example, such a combination may be the simultaneous administration in a cream or eyedrop of VEGF₁₆₅b and acyclovir or similar such agent, for the simultaneous treatment of ocular herpes infection and the corneal angiogenesis that accompanies it. Another such example is the simultaneous administration of VEGF₁₆₅b and an anti-inflammatory agent via intrarticular injection in rheumatoid disease. Another such example is the simultaneous administration of VEGF₁₆₅b and a chemo or immunotherapeutic agent to a tumour condition in a patient.

A further aspect of the invention provides an isolated chemical or biological agent that can inhibit a switch of splicing from sequences described in the said invention to previously described sequences. For example, such an inhibitor could be used to prevent the splicing of a sequence to exclude exon 9. For example, the splicing of mRNA to give VEGF₁₆₅ (which includes exon 8 rather than exon 9) instead of VEGF₁₆₅b (which contains exon 9 rather than exon 8) could be prevented. This would allow the treatment of VEGF₁₆₅-mediated conditions by supplying to a patient the agent that inhibits the switch in splicing from VEGF₁₆₅b to VEGF₁₆₅.

Embodiments of the present invention will now be described, by way of example only, and with reference to the following figures, in which:

FIG. 1 is a diagram showing the mRNA splicing and structure of the VEGF pre-mRNA and positions of relevant PCR primers EX7a, Ex7b, 3′UTR, V165K and V165X. Exon 7a and 3 UTR primers were designed to amplify a 164 bp sequence if VEGF148 was present, 133bp if VEGF 165b was present, a 199bp product if longer splice variants were present, and no band if shorter variants were present. V165K and V165X were designed to amplify to full length product. VEGF165b would result in a 663bp product, VEGF165a 729bp product, VEGF189 an 801bp product and VEGF206 a 852bp product. Exon 7b and 3 UTR were designed to amplify only products from longer splice variants (≧165) but no product from VEGF148.

FIGS. 2A and 2B are photographs of agarose gels containing bands corresponding to PCR products. In FIG. 2A, primers used were 7b and 3′UTR. In FIG. 2B, primers used were 7a and 3′UTR.

FIG. 3A is a photograph of an agarose gel showing the PCR products obtained using exon 7a primer and 3′ UTR primer and mRNA templates obtained from the opposite poles of four human nephrectomy specimens. FIG. 3A shows a PCR of cDNA reverse transcribed from mRNA extracted from four paired renal tissues. Bands were seen at ˜150bp (VEGF165b) in all four benign samples (B1-B4) and two of the malignant tissues (M3-M4), but not in two malignant tissues (M1-M2). Bands were cloned and sequenced from B1-4 and M4).

FIG. 3B is a box plot of the number of tissue samples with a band corresponding to VEGF₁₆₅b (black) or without VEGF₁₆₅b (stippled) in benign and malignant tissues. FIG. 4A is the nucleotide sequence of VEGF₁₆₅ (SEQ ID NO: 19) and VEGF₁₆₅b (SEQ ID NO: 27) cDNA. The 66 bp downstream of exon 7are missing from VEGF₁₆₅b.

FIG. 4B is the exon structure of the C-terminal end of VEGF₁₆₅ and VEGF₁₆₅b. The 3′ UTR sequence of exon 8 contains a consensus intronic sequence for exon 9 , a CT rich region and a CAG immediately prior to the splice site. The nucleotide sequence results in an alternate 6 amino acid C terminus. Capital letters are open reading frames, lower case introns or 3′UTR (italics, VEGF₁₆₅, bold, VEGF₁₆₅b). (SEQ ID NOS 20, 28, 29, 31 & 30 are disclosed respectively in order of appearance).

FIG. 4C is the predicted amino acid sequence of VEGF₁₆₅(SEQ ID NO: 20) compared to VEGF₁₆₅b (SEQ ID NO: 31). The 6 alternative amino acids result in a different C-terminal structure of the VEGF likely to affect receptor activation, but not receptor binding or dimerisation. The Cys is replaced with a Ser and the C terminal amino acids are a basic (underlined) and an acidic (italics) moiety instead of two acidic ones. Therefore the net charge on this end of the molecule will be altered.

FIG. 5A is an agarose gel showing the ˜700 bp PCR product of V165K and V165. The SDS page gel shows the ˜700bp PCR product of V165K and V165X excised from agarose gel and purified.

FIG. 5B is an SDS gel showing the products of nested PCR using excised band as template and exon 7, 3′UTR as primer pairs.

FIGS. 6A-6D show the effect of VEGF165b on HUVEC proliferation. FIG. 6A shows the effect of VEGF_(165b) on VEGF₁₆₅ stimulated HUVEC proliferation. In FIG. 6A ³H-thymidine incorporation per cell was assessed in HUVECs incubated with CM without VEGF (pcDNA), 100 ng/ml. VEGF_(165b), or 100 ng/ml of both (VEGF_(165b)+VEGF₁₆₅), n=3, p<0.01, ANOVA.

FIG. 6B shows dose response studies of the above effect. In FIG. 6B, proliferation index was measured in HUVEC treated with both isoforms compared to that treated with no VEGF₁₆₅ n=3, p=0.001, ANOVA.

FIG. 6C demonstrates the effect of VEGF_(165b) on VEGF₁₆₅ and bFGF stimulated HUVEC_(3H)-thymidine incorporation. In FIG. 6C, ³H-thymidine was incorporated in HUVECs incubated with pcDNA3-CM (stippled), or VEGF_(165b) CM (black bars) with 40 ng/ml VEGF_(165b) or 50 ng/ml bFGF, n=3p<0.01, ANOVA, **=p<0.01, ***=p<0.001 compared to VEGF₁₆₅.

FIGS. 7A and 7B show the effect of VEGF₁₆₅ and VEGF_(165b) on the diameter of rat mesenteric arteries preconstricted with phenylephrine. FIG. 7A shows an example of diameter measurements in a 265pm diameter mesenteric artery. The vessel was constricted with 1 μM Phenylephrine. When perfused with 10 μM acetylcholine the vessel dilated, demonstrating endothelium dependent tone. Dialyzed pcDNA3-CM (CM) did not affect diameter, whereas 20 ng/ml VEGF₁₆₅ (in CM) caused a robust transient vasodilation. VEGF₁₆₅b-CM (40 ng/ml) VEGF₁₆₅b). FIG. 7B shows mean percent vasodilation for 5 vessels, P<0.01, ANOVA, n=5, *=p<0.05 compared to VEGF₁₆₅ SNK post hoc test. The order of perfusions were varied and there was no dependence of the response on the order of perfusion.

FIG. 8 is a photograph of an agarose gel showing the PCR products obtained using exon 9 specific primers and VEGF₁₆₅ and VEGF₁₆₅b templates and annealing temperatures of 58° C. and 60° C. and a range of MgCl₂ concentrations;

FIGS. 9A-9B show detection of synthetic VEGF_(165b). FIG. 9A is a photograph of an agarose gel showing the PCR products obtained using VEGF₁₆₅ and VEGF_(165b) templates and an annealing temperature of 60° C. in PCR competition assays. Lanes 2 and 6 indicate the reactions in which the primers detected VEGF_(165b) in preference to VEGF₁₆₅ when VEGF₁₆₅ was present at 1000.times. the concentration of VEGF_(165b). Isoform specific PCR using exon 9 and exon 4 primers with cloned VEGF_(165b) and VEGF₁₆₅ as template. No amplification was seen in the absence of VEGF_(165b) (lanes 1 & 6) even in the presence of 100 ng VEGF₁₆₅ (lane 6). However, VEGF_(165b) was detected in the absence (lanes 2-5) or presence of (lanes 7-10) of excess VEGF₁₆₅.

FIG. 9B is a photograph of a Western blot showing expression of recombinant VEGF_(165b), VEGF₁₆₅ produced by transfected HEK293 cells and commercial VEGF (Peprotech, N.J., USA). Both isoforms are the same size (˜23kDa) and a small amount of homo-dimerization occurs.

FIGS. 10A and 10B show photographs of agarose gels containing PCR products of a tissue screen in various tissues using primers which detect exon 8 and exon 9 containing (10a) isoforms and Exon 9 specific isoforms (FIG. 10 b); PCR showing expression of exon 9 containing isoforms in various tissues using specific PCR that only detects exon 9 containing isoforms.

FIGS. 11 shows the effect of VEGF_(165b) on VEGF_(165b)-mediated HUVEC migration. Cell migration assessed in HUVECs incubated with pcDNA3-CM (<62.5 pg/ml VEGF), VEGF₁₆₅-CM (33 ng/ml VEGF₁₆₅), VEGF_(165b)-CM (33 ng/ml VEGF_(165b)), or a combination of both CM (33 ng/ml each VEGF isoform). P<0.01, ANOVA, n=6. *=p<0.05, **=p<0.01 compared to VEGF₁₆₅.

FIGS. 12A-12B summarise the sequence identity of exon 9 in different species (SEQ ID NOS 21-23 are disclosed respectively in order of appearance). Sequence identity of Exon 9 and the sequence immediately downstream of exon 9 between different species. FIG. 12A shows that although there is 90% identity (shaded) between human and bovine exon 9 (italics), there is significantly less identity in the equivalent twenty two 3′ base pairs, suggesting that the exon 9 sequence is conserved between species. In the mouse there is a single base pair deletion relative to the human which introduces a frame shift. A second d mutation (C_(mouse)→T_(human)) rescues the stop codon (underlined). FIG. 12B shows a comparison of identity in exon 9 compared to the equivalent number of base pairs immediately 3′ in five different species. *=exon 9 is significantly more highly conserved than the 3′UTR, p<0.01 (X2 test) compared to exon 9 .

FIGS. 13A-13C show PCR products using exon 9 (13a) or exon 8 (13b) specific primers showing VEGF_(165b) mRNA expression in normal, osteoarthritic and rheumatoid synovium, and, (13c) their relative expression. In FIG. 13A, a differential mRNA expression of VEGF_(165b) and VEGF₁₆₅ from normal and arthritic synovial tissue. mRNA was isolated from synovium from patients with non-arthritic (NA), rheumatoid arthritis (RA) and osteoarthritis (OA). In FIG. 13B, relative expression of VEGF_(165b): VEGF₁₆₅mRNA.

FIGS. 14A and 14B show the expression of exon 8 and exon 9 containing VEGF isoforms in individual human pancreatic islets. Heterogeneity can be seen in exon 8 (upper gel) and exon 9 (lower gel) containing VEGF species in individual human pancreatic islets.

FIGS. 15A-15D detail the change in VEGF_(165b) expression in malignant versus benign Trans-urethral resection of prostate curettings. Expression of VEGF_(165b) in TURP chips from BPH and MPC mRNA was extracted from the chips and reverse transcribed using standard methodology and amplified using primers specific to VEGF_(165b). FIG. 15A shows an RT-PCR of RNA extracted from benign prostate chips using primers to detect VEGF_(165b). Eleven of the twelve benign samples showed clear expression of VEGF_(165b). VEGF_(165b) positive controls, and VEGF₁₆₅ negative controls are also shown. The one sample that did not show expression (sample number 12) was also negative for β-microglobulin (i.e. no cDNA was present). FIG. 15B shows an RT-PCR of RNA extracted from malignant prostate chips using primers to detect VEGF_(165b). Only one of the nine malignant samples showed clear expression of VEGF_(165b). VEGF_(165b) positive controls, and VEGF₁₆₅ negative controls are also shown. FIG. 15C shows β-microglobulin expression in the malignant tissues to show that mRNA was effectively purified and reverse transcribed. FIG. 15D shows a percentage of prostates in which TURP chips showed expression of VEGF_(165b) mRNA. P<0.001 (Fisher's Exact Test).

FIG. 16A is a photograph of a gel showing PCR products from archival radical prostatectomy samples. Expression of VEGF_(165b) in sections of paraffin embedded fixed sections of prostate tissue. In FIG. 16A, mRNA was extracted from six 5 μm sections of prostate from histologically defined normal (N), prostate intra epithelial neoplasia (P), or frank carcinoma (C) and reverse transcribed using standard methodology and amplified using primers specific to VEGF_(165b). In FIG. 16B, mean ±SEM densities of 15 PCR products measured using image analysis software. Density of bands are expressed as the percentage of the maximum intensity per patient sample.

FIG. 17 shows the VEGF concentration in media taken from human embryonic kidney cells (HEK293) transfected with 2 μg VEGF₁₆₅b cDNA (in expression vector pcDNA3) alone or with increasing amounts of double stranded siRNA directed across the exon 7-exon 9 splice site.

EXAMPLE 1

Immediately after nephrectomy, cubes of tissue were harvested from the periphery of a macroscopic human kidney tumour and from the benign cortical tissue of the opposite pole of the kidney. 100-200 mg of tissue was homogenised in Trizol reagent and mRNA extracted by addition of chloroform. The tissue was centrifuged and the aqueous layer removed into isopropanol. The mRNA was pelleted and resuspended in 20 μl DEPC treated water. 4 μl of RNA was reverse transcribed using MMLV RT and polydT as a primer. The cDNA was then amplified using 1 μM of the 3′UTR primer (ATGGATCCGTATCAGTCTTCCT)(SEQ ID NO: 3) and 1 μM of primers for either exon 7a (GTAAGCTTGTACAAGATCCGCAGACG)(SEQ ID NO: 4), or exon 7b GGCAGCTTGAGTTAAACGAACG)(SEQ ID NO: 5) , 1.2 mM MgCl₂, 2 mM dNTPs, and 1 unit of Taq polymerase (Abgene) in its buffer. Reactions were cycled 35 times, denaturing at 96° C. for 30 seconds, annealing at 55° C. for 30 seconds, and extending at 72° C. for 60 seconds. The position of annealing of the primers used to the VEGF isoforms is shown in FIG. 1.

PCR products were run on a 3% agarose gel containing 0.5 μg/ml ethidium bromide and visualised under a UV transilluminator. Exon 7a and 3′ UTR primers give a product consistent with VEGF₁₄₈ of 164 bp, and one consistent with VEGF_(165, 183, 189) and ₂₀₆ of 199 bp (see FIG. 2A). Exon 7b and 3′ UTR primers give a product consistent with VEGF_(165, 183, 189), and ₂₀₆ of 130 bp, but no product corresponding to VEGF₁₄₈ (see FIG. 2B). The band at 164 bp was excised from the gel under UV transillumination and the DNA extracted using Qiaex (Qiagen). The DNA was then digested with BamHl and HinDIII and ligated into pBluescriptKSII (Stratagene). Ligations were transformed into supercompetent XL-1 Blue E. coli (Stratagene), and grown on ampicillin resistant LB agar plates. Colonies were amplified and the plasmid DNA purified using Qiagen columns. The DNA was then sequenced using T7 and T3 sequencing primers by fluorescent dideoxy termination sequencing (ABI370). Sequences were analysed by automated fluorescent chromatography, and the sequence checked against the chromatograph by eye.

The resulting sequence is shown in SEQ.ID No. 4. In four of the samples the normal tissue had significantly more ˜150 bp product than ˜200 bp product. One of these samples was used to confirm the full length of the new isoform. The entire length of the product was amplified by RT-PCR using primers downstream of the original 3′UTR primer (V165X, AAT CTA GAC CTC TTC CTT CAT TTC AGG) (SEQ ID NO: 6) engineered with an Xbal site, and a primer complementary to the translation intitiation site of the other isoforms of VEGF (V165K, CCG GTA CCC CAT GAA CTT TCT GC) (SEQ ID NO: 7) engineered with a Kpnl site and PCR conditions as previously described.

PCR was carried out using exon 7b and 3′ UTR primers or exon 7a and 3′ UTR primers and a selection of mRNAs purified from the opposite poles of four human kidneys as template RNA. By using opposite poles of the kidneys, both malignant tissue (at one pole) and benign tissue (at the other pole) samples were obtained from each of the four human kidneys studied. The PCR used the same reaction conditions as previously described.

A sample of the results can be seen in FIG. 3. Of eighteen kidneys, 17 had detectable levels of expression of a VEGF isoform consistent with VEGF_(148B) in the benign tissue, whereas only 4 of the 18 kidney samples (p<0.001, Fishers Exact Test) had detectable levels of expression in the malignant tissue. Subsequent sequencing of this VEGF isoform revealed an unexpected 3′ sequence (FIG. 4). The sequence indicated that the mRNA was spliced from the 3′ end of exon 7into the 3′ untranslated region of VEGF₁₆₅ mRNA+44 bp from the end of exon 8 . This splice site has the same first two nucleotides as exon 8 , but a different 3′ sequence (see FIG. 4A), which has been designated exon 9 . The intronic region between exon 7 and exon 9 has an intronic consensus sequence of 5′GT . . . CAG3′ and a high CT rich region 6-24 bp prior to the 5′ end of exon 9 . PCR of the full length product using primers V165K and V165X resulted in one strong band at approximately 670 bp. Further, nested PCR using the 3′UTR and 7a primers described above resulted in a strong band at 133 bp, confirming that the full length was VEGF _(165b). Cloning of the full length of this sequence and subsequent sequence analysis using one of the clones (clone 1) revealed a 663 nucleotide sequence with a single open reading frame encoding a peptide 191 amino acids long. This peptide consisted of the same N terminal 185 amino acids as VEGF₁₆₅ (i.e. a 26 amino acid signal sequence followed by 159 amino acids corresponding to exons 1, 2, 3, 4, 5 and 7). However, the C terminal 6 amino acids were not the same as exon 8 (see FIG. 4B). The six amino acids that this new exon codes for are Ser-Leu-Thr-Arg-Lys-Asp (SEQ ID NO: 9), followed by a stop codon, TGA. Since this splice variant would code for a mature 165 amino acid polypeptide (after cleavage of the signal sequence) with 96.4% identity with VEGF₁₆₅, this isoform has been designated VEGF_(165b).

The region between exon 7 and exon 9 that has been spliced out in VEGF₁₆₅b includes 66 bp making up exon 8 and the first 44 bp of the 3′UTR of VEGF₁₆₅. Therefore, the PCR product resulting from VEGF₁₆₅b and exon 7+3′UTR primers is 66 bp shorter than VEGF₁₆₅, hence the lower band seen on the gel in FIG. 3 a which corresponds to the new VEGF isoform.

VEGF₁₄₈ lacks 35 nucleotides of exon 7, but retains the exon 8 nucleotide sequence (which remains untranslated due to the introduction of a stop codon due to a frame shift) and the untranslated region between exons 8 and 9, and the UTR 3′ to exon 9. Therefore, the PCR product of VEGF₁₄₈ and exon 7+3′UTR primers would only be 31 bp shorter than the VEGF₁₆₅b PCR product using the same primers, hence the original observation that the lower band on the gel is consistent with VEGF148. However, the lower band, in fact, corresponds to new isoform VEGF₁₆₅b.

Exons 8 and 9 both code for 6 amino acids and a stop codon. The amino acid sequences are completely different. Exon 8 encodes for CDKPRR (SEQ ID NO: 24). The cysteine forms a disulphide bond with Cys146 in exon 7. This results in the carboxy terminus of VEGF₁₆₅ being held close to the receptor binding domain in exon 3 in the three dimensional structure of VEGF. In addition the proline inserts a kink in the amino acid backbone of the molecule to further appose the final three amino acids at the receptor binding domain. Finally the two terminal amino acids are highly positively charged arginine residues. These charged residues will be held very close to the receptor binding and in the crystal structure of the receptor ligand complex appear to be in a position to interact with the receptor. This, indicates that these amino acids may be necessary for receptor stimulation. Exon 9 on the other hand codes for SLTRKD (SEQ ID NO: 9) and has lost the cysteine residue and therefore the carboxy terminus may not be held into the receptor binding site. In addition there is no proline kink, and therefore the terminal two amino acids may not be able to interact with the receptor. It may therefore be possible that VEGF_(165b) will bind to the VEGF receptor but not activate it. This theory arises since VEGF _(165b) contains all the elements required for i) efficient dimerisation B Cys² and Cys⁴ in exon 3 (21); ii) receptor binding B for VEGFR1 Asp63, Glu64, Glu67 in exon 3 , for VEGFR2 Arg82, Lys84, His 86 in exon 4 , and for neuropilin-1 Cys136 to Cys158 in exon 7. This isoform substitutes exon 9 for exon 8 and therefore has no Cys159 which normally binds to Cys146 in exon 7, and will therefore be likely to affect the folding and tertiary structure of the VEGF molecule.

The fact that this isoform has been found specifically in the kidney is particularly interesting as the kidney, and in particular the glomerulus has been shown to produce high levels of VEGF. This has always been assumed to be VEGF₁₆₅, since it is detected by antibodies to VEGF₁₆₅, in situ hybridisation using probes to VEGF₁₆₅, PCR using primers specific to VEGF₁₆₅ and so on. However, in almost all these cases the detection techniques used would not distinguish between VEGF₁₆₅ and VEGF₁₆₅b. The only reason that VEGF₁₆₅b has been detected now is that an attempt was being made to examine VEGF₁₄₈ expression in this tissue. It is interesting that, despite high levels of VEGF produced by podocytes in the glomerulus, glomerular endothelial cells, which do express VEGF receptors, are not of an angiogenic phenotype. Endothelial cell turnover in the glomerulus is low, as in other parts of the body, and there is no overt angiogenesis occurring. This apparent paradox—high VEGF expression but low angiogenesis—may be explained by VEGF₁₆₅b. Kidney tumours must grow in an environment in which VEGF is highly expressed under normal conditions, and yet angiogenesis is prevented. Therefore tumours need to overcome some endogenous anti-angiogenic process in order to grow. If VEGF₁₆₅b is inhibitory then the down regulation of VEGF₁₆₅b by tumours, as shown here, would be necessary for tumours to switch angiogenesis on in this tissue. Furthermore, the high production of VEGF by the glomerulus may actually be VEGF₁₆₅b rather than VEGF₁₆₅, and therefore this would explain why angiogenesis is not observed.

A further clone (clone 2) containing the full length PCR product (obtained using primers V165K and V165X) was selected and sequenced. Surprisingly, although this sequence contained the same C terminal 6 amino acids as clone 1, indicating the presence of exon9, the full length of the cloned sequence was longer than that of the sequence of clone 1, i.e. longer than 670 bp and therefore not consistent with VEGF₁₆₅b. In fact, the sequence length was found to be slightly over 700 bp, which is more consistent with VEGF₁₈₃b (see FIG. 5). FIG. 5B shows the products of nested PCR using the excised ˜700 bp band as template and exon 7 and 3′UTR as primer pairs.

It therefore seems that a family of VEGF isoforms may exist which posses exon 9 in place of exon 8. The existence of VEGF₁₆₅b has been demonstrated in the example provided herein and and evidence for VEGF₁₈₃b is presented. However, it is likely that similar isoforms exist which correspond to VEGF₁₂₁, VEF₁₄₅, VEGF₁₈₉, VEGF₂₀₆, designated VEGF₁₂₁b, VEGF₁₄₅b, VEGF₁₈₉b and VEGF₂₀₆b. These isoforms which lack exon 8 are all expected to demonstrate anti-angiogenic activity.

TABLE 1 Expected PCR product size for V165K and V165X primers for the different splice variants of VEGF. No of amino acids 121 145 148 165 183 189 206 No of VEGF_(XXX) 597 669 694 729 783 801 852 nucleotide VEGF_(XXX)b 531 603 628 663 717 735 786 s3′

EXAMPLE 2

In separate transfections, full length VEGF₁₆₅b cDNA and full length VEGF₁₆₅ cDNA were cloned into pcDNA3 using standard methodology, and then transfected into HEK 293 cells and a stable cell line generated using Geneticin selection. Confluent cells were incubated in basal M200 endothelial cell medium for 48 hours containing neither serum nor Geneticin, and the conditioned media assayed for VEGF concentration using a pan VEGF ELISA (R & D Systems). Control (mock) conditioned media (pcDNA3-CM) was collected in the same way from HEK293 cells transfected with pcDNA3 only.

Freshly isolated HUVECs incubated in 0.1% serum M200 overnight were incubated with either pcDNA3-CM, VEGF₁₆₅-CM (adjusted to 100 ng/ml VEGF₁₆₅ with pcDNA3-CM), VEGF₁₆₅b-CM (adjusted to 100 ng/ml VEGF₁₆₅b with pcDNA3-CM) or a mixture of VEGF₁₆₅b-CM and VEGF₁₆₅-CM (adjusted to 100 ng/ml VEGF₁₆₅b and 100 ng/ml VEGF₁₆₅ with pcDNA3-CM), and then 37 kBq of ³H-Thymidine (Amersham Pharmacia) added. After 4 hrs the cells were washed, trypsinised, cell number counted on a hemocytometer and radioactivity measured on a beta counter (LKB-1217). Incorporation was calculated as counts per cell. Dose response curves were carried out in a similar manner, except that VEGF₁₆₅b-CM was diluted with pcDNA3-CM and 50ng/ml VEGF₁₆₅ (Peprotech, N.J.) added. Proliferation index was calculated as ³H-thymidine incorporation of VEGF₁₆₅ treated cells compared to mean incorporation into cells with no VEGF₁₆₅ treatment.

To determine the functional effect of VEGF₁₆₅b we measured endothelial cell proliferation by determination of ³H-thymidine incorporation per cell number during incubation with conditioned media from transfected cells (FIG. 6). The full-length cDNA generated by PCR was cloned into an expression vector (pcDNA3-VEGF₁₆₅b), as was full length VEGF₁₆₅ (pcDNA3-VEGF₁₆₅) and each transfected into HEK293 cells. The VEGF concentration of cell conditioned media (VEGF₁₆₅b-CM), as determined by ELISA using pan VEGF antibodies, ranged from 80-400 ng/ml VEGF. Conditioned media from cells transfected with pcDNA3-VEGF₁₆₅ (VEGF₁₆₅-CM) had a VEGF concentration of 100-260 ng/ml. Media from cells transfected with pcDNA3 alone (pcDNA3-CM) contained <62.5 pg/ml VEGF (the minimum detection limit of the ELISA). HUVECs were incubated in VEGF₁₆₅-CM adjusted to 100 ng/ml (with pcDNA3-CM) and this resulted in a significant 283±43% increase in thymidine incorporation per endothelial cell compared to pcDNA3-CM alone (P<0.01, ANOVA, FIG. 6 a). VEGF₁₆₅b-CM containing 100 ng/ml VEGF₁₆₅b did not stimulate HUVEC proliferation (165±27% of pcDNA3-CM, no significant increase, but significantly less than VEGF₁₆₅-CM, p<0.05). Furthermore, there was no increase in endothelial cell proliferation when cells were incubated in a combination of both VEGF₁₆₅b-CM and VEGF₁₆₅-CM containing 100 ng/ml of each VEGF isoform (150±18% of pcDNA3-CM, not significantly different from pcDNA3-CM, but significantly lower than VEGF₁₆₅-CM, p<0.05). Therefore VEGF₁₆₅b did not stimulate HUVEC proliferation, and moreover, significantly inhibited VEGF₁₆₅ stimulated proliferation. Furthermore when endothelial cells were incubated in CM containing increasing concentrations of VEGF₁₆₅b there was a dose dependent inhibition of ³H-thymidine incorporation stimulated by commercially available VEGF₁₆₅ (FIG. 6 b), with a molar ratio IC₅₀ of 0.94 (FIG. 6 d) (i.e. equimolar inhibition). Additionally, VEGF₁₆₅b-CM did not affect FGF mediated proliferation (FIG. 6 c).

EXAMPLE 3

The effect of VEGF₁₆₅b on VEGF₁₆₅-mediated vasodilatation was determined as detailed below.

3^(rd) order superior mesenteric arteries were dissected from 200-300 g male Wistar rats (sacrificed by stunning and cervical dislocation) and leak-free segments mounted in an arteriograph at 80 mmHg, in M200 media10 mm acetylcholine (Ach) maximally dilated all arteries used in this example, demonstrating the presence of an intact endothelium.

The rat mesenteric arteries were preconstricted with 0.6-1 μm phenylephrine (PE) applied in the superfusate (see FIG. 7A). Ach, CM and VEGF isoforms (all dialysed against rat ringer solution using 3500 MW dialysis tubing) were then applied to the lumen of the artery using an adaptation of the Halpern pressure myograph technique as described in Doughty, J. M. et al (1999) Am J Physiol 276, 1107-12. The concentration of VEGF in the CM after dialysis was determined by ELISA. All data are expressed as mean values ± s.e. mean for 4 experiments. Statistical significance was tested using ANOVA and Student Newmann Keuls post-hoc test.

We measured the effects of VEGF₁₆₅b on vasodilatation to determine whether VEGF₁₆₅b could inhibit the effects of VEGF₁₆₅ on intact vessels. Luminal perfusion of isolated pressurized rat mesenteric arteries in vitro with pc-DNA3-CM resulted in no change in vessel diameter (FIG. 7). Perfusion of the same arteries with dialyzed VEGF₁₆₅b-CM (40 ng/ml) did not affect the diameter of the arteries either. Perfusion with dialyzed CM containing 20 ng/ml VEGF₁₆₅ resulted in significant vasodilatation, but this vasodilatation was abolished when perfused with VEGF₁₆₅b-CM and VEGF₁₆₅ (40 ng/ml VEGF₁₆₅b, 20 ng/ml VEGF165). Therefore VEGF₁₆₅b does not stimulate vasodilatation, and is also capable of inhibiting VEGF₁₆₅-mediated vasodilatation.

EXAMPLE 4

As mentioned earlier, the kidney, and in particular the glomerulus, has been shown to produce high levels of VEGF. This has always been assumed to be VEGF₁₆₅, since it is detected by antibodies to VEGF₁₆₅, or by in situ hybridisation using probes to VEGF₁₆₅, or by PCR using primers specific to VEGF₁₆₅.

However, in all of these cases, the detection techniques used would not distinguish between VEGF₁₆₅ and VEGF₁₆₅b.

A method of detection of VEGF₁₆₅b mRNA independently of VEGF₁₆₅ mRNA has been developed and is detailed below (FIGS. 8 and 9A).

PCR was carried out using vectors containing VEGF₁₆₅ and VEGF₆₅b, respectively, and the following primers:

Forward primer Exon-4 GAGATGAGCTTCCTACAGCAC (SEQ ID NO: 1) Reverse Primer 9H TTAAGCTTTCAGTCTTTCCTGGTGAGAGATCTGCA (SEQ ID NO: 2)

The annealing and denaturing steps were carried out for 30 seconds and denaturing was carried out at 94° C. 1 minute periods of extension were carried out at 72° C.

As can be seen from FIG. 8, when an annealing temperature of 58° C. is used, PCR products are obtained for both VEGF₁₆₅ and VEGF₁₆₅b. However, when an annealing temperature of 60° C. is used, there is no cross-reactivity and no PCR product corresponding to VEGF₁₆₅ is obtained.

Competitive PCR studies were carried out using the PCR primers and conditions mentioned above, with the annealing step being carried out at 60° C. The samples used contained VEGF₁₆₅ and VEGF₁₆₅b at various relative concentrations, as shown in FIG. 9 a. FIG. 9 a demonstrates that, even when VEGF₁₆₅ is present in the sample at 1000 times the concentration at which VEGF₁₆₅b is present, the only PCR product obtained corresponds to amplification of VEGF₁₆₅b and not VEGF₁₆₅.

Therefore, the above primers can be used to detect VEGF₁₆₅ and VEGF₁₆₅b in a sample. Further, by altering the temperature at which the PCR annealing step is carried out, the same primers can be used to specifically detect the presence of VEGF₁₆₅b in a sample containing both VEGF₁₆₅ and VEGF₁₆₅b.

EXAMPLE 5

Full length VEGF₁₆₅b or VEGF₁₆₅ (generated by PCR from tissue) was cloned into the expression vector pcDNA₃ using standard methodology, and then transfected into HEK 293 cells and a stable cell line generated using Geneticin selection. Confluent cells were incubated in basal M200 endothelial cell medium for 48 hours, containing neither serum nor Geneticin, and the conditioned media assayed for VEGF concentration using a pan VEGF ELISA(R&D). Control conditioned media (pcDNA3-CM) was collected in the same way from HEK293 cells stably transfected with pcDNA₃. FIG. 9 b shows a Western blot of conditioned media from VEGF₁₆₅b transfected cells (VEGF₁₆₅b-CM) and VEGF₁₆₅ transfected cells (VEGF₁₆₅-CM). VEGF₁₆₅b was the same molecular weight as VEGF₁₆₅, and both isoforms correspond to previously published molecular weights for VEGF₁₆₅ (Ferrara N et al Biophys. Res. Comm. 1989; 161: 851-8). The blot also confirms that most of the VEGF₁₆₅ and VEGF₁₆₅b made in HEK cells had a slightly greater molecular weight than commercially available VEGF₁₆₅ (23 kDa compared to 18 kDa). This is probably due to the fact that commercially available VEGF₁₆₅ is not glycosylated. There was some VEGF₁₆₅b and VEGF₁₆₅ in the conditioned media that appeared to be de-glycosylated, but this was a small fraction of the total VEGF.

EXAMPLE 6

mRNA from sixteen different tissues was reverse transcribed and amplified using exon 7 and 3′UTR primers. PCR products of lengths consistent with expression of exon 9 containing isoforms were clearly detected in umbilical cord, cerebrum, aorta, prostate, pituitary, lung, skeletal muscle and placental tissue as well as kidney (see FIG. 10A). Fainter bands were also seen in colon, skin, bladder and spinal cord. No significant exon 9-containing isoforms were detected in the hypothalamus, inferior vena cava (IVC), or liver. Subsequent PCR using exon 9-specific primers confirmed the distribution of expression in the different tissues (see FIG. 10B), but in this case expression was detected in liver, and expression in the pituitary was marginal. Interestingly in aorta, prostate and umbilical cord a slightly longer band was seen. It is not clear whether these are additional exon 9-containing isoforms such as VEGF₁₈₃b and/or VEGF₁₈₉b.

EXAMPLE 7

In order to assess the functional properties of VEGF₁₆₅b on endothelial cell migration, migration assays were performed in a modified 24-well Boyden chamber containing collagen coated polycarbonate filter inserts (8 μm pore; Millipore). The filters were placed in 24 well plates containing 0.5 ml per well of either 1) VEGF₁₆₅-CM containing 33 ng/ml VEGF₁₆₅; 2) VEGF₁₆₅b-CM containing 33 ng/ml VEGF₁₆₅b; 3) VEGF₁₆₅-CM and VEGF₁₆₅b-CM (33 ng/ml of each isoform); or 4) pcDNA₃-CM CM. HUVECs were suspended in serum free medium and 25,000 cells added to the upper chamber of each well. The plate was incubated for 6 h to allow migration, media removed and both chambers washed with PBS (×2). 0.2 mg/ml Thiazolyl Blue (MTT) in media was then added to both chambers and incubated for 3 h at 37° C. The media was removed and the chambers were washed with PBS (×2). Non-migrated cell crystals in the upper chamber (stained blue) were removed with a cotton swab, which was placed in 1 ml of Dimethyl Sulphoxide (DMSO) to dissolve the MTT product. Migratory cell crystals (on the underside of the insert) were also dissolved in MTT. The samples were left overnight to permit complete solution of the product. The absorbance of soluble MTT was determined at a wavelength of 570 nm using a spectrophotometer. The percentage migration was then calculated from the intensity of the lower well as a percentage of the total intensity of both wells. Assays were run in sextuplet.

HUVECs were incubated in VEGF₁₆₅-CM (33 ng/ml VEGF₁₆₅) and this resulted in a significant 24±3% increase in migration of endothelial cells compared to pcDNA3-CM alone (P<0.01, ANOVA)(FIG. 11). VEGF₁₆₅b -CM containing 33 ng/ml VEGF₁₆₅b did not stimulate migration (−3±2.6% compared to pcDNA3-CM, not significant). Furthermore, there was no increase in migration when cells were incubated in a combination of both VEGF₁₆₅b-CM and VEGF₁₆₅-CM containing 33 ng/ml of each isoform (9.9±5.8% compared to pcDNA3-CM). Therefore VEGF₁₆₅b did not stimulate migration, and again significantly inhibited VEGF₁₆₅-stimulated migration (P<0.001, ANOVA).

EXAMPLE 8

A search of the nucleotide database provides interesting information on the conservation of the 3′ untranslated region (3′UTR). The entire 3′ UTR from the end of exon 8 is 100% conserved between human and macaque. In other mammalian species there is relatively good conservation of the supposed 3′ UTR terminal to exon 8 (FIG. 12). In fact, in the cow the mRNA has >95% identity in the 66 bases 3′ to the stop codon of exon 8 , and exon 9 is >90% identical. However, this identity breaks down immediately after the exon 9 stop codon (see FIG. 12). There is significantly less identity in the 22 bases after this stop codon (53%) than that in exon 9 (91%). This pattern is also evident in mouse where the exon 9 containing sequence is 86% identical to human, but only 23% identical in the 22 base pairs immediately after the exon 9 stop codon (see FIG. 12). Interestingly the mouse sequence predicts an exon 9 of 7 amino acids of the sequence PLTGKTD (SEQ ID NO: 8), compared to SLTRKD (SEQ ID NO: 9) in the human and macaque and RLTRKD (SEQ ID NO: 10) in the cow. Therefore 4 out of six amino acids are conserved [XLTXK(X)D] (SEQ ID NO: 25) and this appears to have been brought about by a double mutation—an adenosine insertion in the human at nucleotide 10 (mouse) and a cytosine to thymidine mutation at nucleotide 19 (mouse) that rescues the stop codon (see FIG. 12). This is indirect evidence for functional relevance of the splice site. Interestingly it is only conserved in mammals, not in birds or fish.

EXAMPLE 9

VEGF has been shown to be massively upregulated in arthritis, particularly in synovial fibroblasts, macrophages and synovial lining cells (Nagashima M et al, 1995; J Rheumatol 22: 1624-30). Furthermore there is now mounting functional evidence that inhibition of angiogenesis, both non-specifically with pharmacological anti-angiogenic agents (Oliver S et al Cell Immunol 1994; 157: 291-9; Oliver S. et al Cell Immunol 1995; 166: 196-206), and specifically with anti-VEGF agents, ameliorates the joint lesions in well characterised animal models of arthritis (Miolta J et al Lab Invest 2000; 80: 1195-205; Sone H et al Biochem Biophys Res Commun 2001; 281: 562-8). Using an RT-PCR protocol described under example 6, VEGF₁₆₅b expression has been identified in human synovium (taken at operation from a patient who suffered a fractured neck of femur secondary to osteoporosis). VEGF₁₆₅b expression was shown to be present in normal human synovium collected from the Bristol University Anatomy Department. In order to obtain preliminary data on the expression of VEGF₁₆₅b mRNA in normal and arthritic tissue, RT-PCR was carried out on two previously available samples of osteo tissue and two of rheumatoid tissue (see FIG. 13). Interestingly VEGF₁₆₅b was found in three of these four samples, but at a lower level than VEGF₁₆₅. This was in stark contrast to normal tissue which had at least as much VEGF₁₆₅b as VEGF₁₆₅. The ratio of VEGF₁₆₅b to VEGF₁₆₅ mRNA in synovium was therefore, lower in rheumatoid arthritis than osteoarthritis, and lower in osteoarthritis than normal tissue. This suggests that in arthritis the anti-angiogenic properties of VEGF₁₆₅b also are reduced.

EXAMPLE 10

Human islet transplantation offers a unique therapeutic option in the management of the metabolic and vascular sequelae of diabetes mellitus. However animal models and clinical experience suggest that transplanted islet function is not predictable in an individual recipient. It has been suggested that the initial function of transplanted islets is dependent on their ability to access the recipient vascular system by the stimulation of microvascular angiogenesis.

Human islets were purified by collagenase digestion (Liberase HI, Roche Diagnostics) and continuous density gradient centrifugation on a Cobe 2991 cell separator. Individual islets were then collected in 20 μl diethylpyrocarbonate (depc) H₂O in separate tubes. Each sample was homogenized in Trizol reagent and mRNA was extracted according to the manufacturers' instructions. mRNA was reverse transcribed using polyd(T) as a primer and ExpandRT (Roche). Exon 8 and exon 9 containing VEGF isoforms were studied in 11 individual islets. A heterogeneity of expression of both VEGF families was identified (see FIG. 14). It is believed that the balance of pro- and anti-angiogenic VEGF isoform expression by transplanted islets may determine the survival of individual islets and hence the overall efficiency of the graft. Inhibition of the activity of anti-angiogenic VEGF₁₆₅b may therefore enhance graft survival and function.

EXAMPLE 11

In order to assess if VEGF₁₆₅b expression is altered in cancers other than renal cancer, VEGF₁₆₅b expression was studied in prostate.

VEGF₁₆₅b expression was studied in trans-urethral prostatectomy curettings using the PCR protocol described under example 6 (Exon specific primers). VEGF₁₆₅b was present in significantly less malignant samples compared to benign (FIG. 15).

In addition, we studied VEGF₁₆₅b expression in archival radical prostatectomy samples to determine the expression of VEGF165b in the early stages of prostate cancer, i.e. in prostatic intra-epithelial neoplasia (PIN)(see FIG. 16). Significant down regulation of VEGF165b mRNA was seen in PIN lending credence to the hypothesis that the angiogenic switch in prostate cancer may result from an imbalance of pro and anti-angiogenic VEGF isoforms. The template mRNA was obtained from archival tissue using a standard protocol (Krafft A E I et al. (1997); 2(3); 217-230).

EXAMPLE 12

To assess the possibility of specifically inhibiting the VEGF₁₆₅b isoform, small interference RNAs to the exon7-exon9 boundary were developed.

siRNA probes may be made according to the art from primers for example of the sequence:

T7siRNA165bsR 5′ AGAGATCTGCAAGTACGTTCTATAGTGAGTCGTATTA 3′ (SEQ ID NO: 11) T7siRNA165basR 5′ ACGAACGTACTTGCAGATCTCTATAGTGAGTCGTATTA 3′ (SEQ ID NO: 12) siRNA165bF 5′ TAATACGACTCACTATAG 3′ (SEQ ID NO: 13)

These are T7 small interfering RNA for VEGF₁₆₅b sense reverse primer, T7 small interfering RNA for VEGF₁₆₅b antisense reverse primer and small interference RNA for VEGF₁₆₅b forward primer, respectively.

Production of double stranded DNA duplexes from T7siRNA165bsR and T7siRNA165bF provide templates for sense RNA, and production of double stranded DNA duplexes from T7siRNA165basR and siRNA165bF provide templates for antisense RNA.

Annealing of these two RNAs results in the production of a double stranded siRNA duplex with overhang of the sequence (SEQ ID NOS 14 & 26, respectively in order of appearance):

5′  GAACGUACUUGCAGAUCUCUC 3′     ||||||||||||||||||| 3′UGCUUGCAUGAACGUCUAGAG   5′

This double stranded siRNA duplex, when transfected into cells, will reduce VEGF₁₆₅b production, as shown in FIG. 17.

(SEQ ID NO: 9)- Amino acid sequence of Exon 9 SLTRKD SEQ ID NO: 16)- Nucleotide sequence of Exon 9 ATCTCTCACCAGGAAAGACTGA (SEQ ID NO: 17)- Amino acid sequence of VEGF₁₆₅b

MNFLLSWVHW SLALLLYLHH AKWSQAAPMA EGGGQNHHEV VKFMDVYQRSYCHPIETLVD IFQEYPDEIE YIFKPSCVPL MRCGGCCNDE GLECVPTEESNITMQIMRIK PHQGQHIGEM SFLQHNKCEC RPKKDPARQE NPCGPCSERRKHLFVQDPQT CKCSCKNTDS RCKARQLELN ERTCR SLIRK D

(SEQ ID NO: 18) - Nucleotide sequence of VEGF₁₆₅b ATGA ACTTTCTGCT GTCTTGGGTG CATTGGAGCC TTGCCTTGCT GCTCTACCTC CACCATGCCA AGTGGTCCCA GGCTGCACCC ATGGCAGAAG GAGGAGGGCA GAATCATCAC GAAGTGGTGA AGTTCATGGA TGTCTATCAG CGCAGCTACT GCCATCCAAT CGAGACCCTG GTGGACATCT TCCAGGAGTA CCCTGATGAG ATCGAGTACA TCTTCAAGCC ATCCTGTGTG CCCCTGATGC GATGCGGGGG CTGCTGCAAT GACGAGGGCC TGGAGTGTGT GCCCACTGAG GAGTCCAACA TCAGCATGCA GATTATGCGG ATCAAACCTC ACCAAGGCCA GCACATAGGA GAGATGAGCT TCCTACAGCA CAACAAATGT GAATGCAGAC CAAAGAAAGA TAGAGCAAGA CAAGAAAATC CCTGTGGGCC TTGCTCAGAG CGGAGAAAGC ATTTGTTTGT ACAAGATCCG CAGACGTGTA AATGTTCCTG CAAAAACACA GACTCGCGTT GCAAGGCGAG GCAGCTTGAG TTAAACGAAC GTACTTGCAG ATCT CTCACCAGGA AAGACTGA 

1. An isolated VEGF polypeptide comprising an amino acid sequence at least 95% identical to the C-terminal 165 amino acid sequence from SEQ ID NO:17, wherein the polypeptide inhibits pro-angiogenic VEGF receptor activity.
 2. The isolated VEGF polypeptide of claim 1, wherein the amino acid sequence is identical to the C-terminal 165 amino acid sequence from SEQ ID NO:17.
 3. The isolated VEGF polypeptide of claim 1, wherein the mature VEGF polypeptide comprises amino acid sequence SLTRKD (SEQ ID NO:9) at the C-terminus.
 4. An isolated mature VEGF polypeptide, the polypeptide comprising an amino acid sequence corresponding to exons 1-2-3-4-5-7 of VEGF165 linked directly to amino acid sequence SLTRKD (SEQ ID NO:9) at the C-terminus.
 5. A method for preventing or reducing VEGF-mediated cell proliferation in a mammalian patient comprising supplying to the patient a polypeptide comprising the sequence of an isolated VEGF polypeptide according to claim 1 or 4 in an amount that prevents or reduces VEGF-mediated cell proliferation.
 6. A pharmaceutical composition comprising a VEGF polypeptide according to claim 1 or 4 and a pharmaceutically acceptable diluent.
 7. A method of inhibiting angiogenesis comprising administering to a subject in need thereof an isolated VEGF polypeptide comprising an amino acid sequence at least 95% identical to the C-terminal 165 amino acid sequence from SEQ ID NO:17, wherein the polypeptide inhibits pro-angiogenic VEGF receptor activity.
 8. The method of claim 7, wherein the subject is suffering from a disease selected from the group consisting of tumor growth and metastasis, rheumatoid arthritis, neointimal hyperplasia, diabetic retinopathy, retrolental fibroplasia, neovascular glaucoma, age-related macular degeneration, hemangiomas, corneal angiogenesis associated with ocular injury or infection, vascular disease, and psoriasis. 